The principal objective is to investigate the pathophysiological effects of trace metals. Cadmium is the one under most intensive investigation at the moment, particularly its hypertensive effects. The effects on hematology, cardiovascular function, electrolyte composition of the body fluids, organ histology and blood pressure are being examined, principally in the rat. Different dosages and various routes of administration are being tested. The relationship of the acute pressor response to parentially administered cadmium, about which there is no question, to the chronic hypertensive state, which some investigators contend is induced, but which others have failed to confirm, is in particular focus. Different rat strains of both sexes and at various ages are being tested under a variety of experimental protocols.